Thermoplastic sheets are used in a variety of industries as a part of weatherproofing systems and landfill and spill containment systems. For example, thermoplastic sheets are often used to make tarps used to protect the material carried by trucks, trains or other vehicles hauling cargo. For many systems, it is necessary to form a weld between the edges of two adjacent thermoplastic sheets. The welds may be used to join two sheets to create a larger thermoplastic sheet, or other seams as required by the particular application. Typically, seams are created by heating the edges of adjacent sheets of thermoplastic above the melting point of the material and then mating and compressing the heated surfaces together.
A variety of thermoplastic welding devices are commercially available. Some of these devices are hand held units that can be used in a field application to join adjacent thermoplastic sheets, and others are stationary units that are typically used in factory settings to produce thermoplastic products. In stationary welding devices it is known to use a heating wedge to heat the thermoplastic sheets above the melting point of the thermoplastic, and then to apply pressure to the heated sheets to bond them together. The edges of the thermoplastic sheets are drawn over and across the heating wedge and into contact with one-another immediately after being heated and prior to cooling. While this technique can be effective in producing consistent high quality welds, the speed at which the welding is performed is relatively slow. The thermoplastic must be drawn across the heating wedge slowly in order to reach the required temperatures to bond with the adjacent sheet.
Thus, the need exists for a thermoplastic sheet welding device that produces consistent high quality welds at an increased rate of speed.